In the production of photographic printing plates, it is necessary to establish a system to form an image having high contrast in order to ensure reproducibility of an image of continuous gradation by dot images or reproducibility of line images.
For this purpose, a special type of developer, generally called a lith developer, has hitherto been employed. The lith developer generally contains only hydroquinone as a developing agent, and also contains, as a preservative, a sulfite in the form of an adduct with formaldehyde at an extremely reduced concentration of free sulfite ions, so as not to inhibit infectious developability of the developing agent. Therefore, the lith developer has a serious disadvantage in that it is susceptible to air oxidation and cannot withstand storage without deterioration over a period of more than 3 days.
Conventional methods for obtaining a photographic property of high contrast by using a stable developer include a method of using a hydrazine derivative as disclosed in U.S. Pat. Nos. 4,166,742, 4,168,977, 4,221,857, 4,224,401, 4,243,739, 4,272,606 and 4,311,781, etc. This method can afford good photographic properties such as high contrast and high sensitivity, and also permits addition of highly concentrated sulfite to a developer, so that the developer has a greatly improved stability against air oxidation as compared with the lith developer.
However, the effects of increasing contrast and sensitivity brought about by the hydrazine derivative are apt to vary with variation of chemical properties of a developer. Therefore, very complicated management has been required in order to attain invariably stable effects and to increase contrast and sensitivity, particularly in the case when the development is conducted using an automatic developing machine. For example, the amount of silver contained per unit surface area of the development-processed light-sensitive material and the blackened ratio should be determined each time a light-sensitive material is processed, and the developer should be replenished accordingly.